“יהוה appeared to him (Avraham)” Genesis 18:1
“Looking up, he (Avraham) saw three figures standing near him. Perceiving this, he ran from the entrance of the tent to greet them” Genesis 18:2
God appears before Avraham, about to tell Avraham something, however, Avraham at the same time sees three strangers.
Who will Avraham attend to? Who would you choose to greet first?
Avraham choses the strangers, teaching us (As Maimonides comments on this verse) that hospitality to strangers surpasses attending to God.
Humans come first, always.